Editor's Note: Inc.'s 12th annual 30 Under 30 list features the young founders taking on some of the world's biggest challenges. Here, meet Accion Systems.

Natalya Bailey's journey into aerospace engineering and later the jet propulsion business began as many do, with aliens.

The 30-year-old grew up rural Oregon, where the stars at night are big and bright. Some of the stars wandered, she noticed; those were satellites. Others made a canopy so dense with other suns that she didn't wonder if life existed elsewhere in the universe, she knew that it must, and she became obsessed with aliens. When Bailey realized she had a knack for numbers, "I think just some practical bone in me, or my family, encouraged me to not just pursue aliens but maybe combine that with math," she says, "and I arrived at engineering."

Louis Perna--Bailey's eventual co-founder--was perhaps less dreamy as a child. The 29 year-old's favorite toy growing up was a snap-together Space Shuttle. He liked model rockets, and radio-controlled airplanes, and when he grew up and went away to college, and was exposed to the different disciplines within aerospace, "the one that always was just fascinating to me," he says, "was watching things go fast and explode."

Bailey's and Perna's paths crossed in 2011 at MIT's Jet Propulsion Laboratory. Both were drawn to a specific technical challenge that arose with the recent revolution in satellite technology. To wit: Once you replace the billion-dollar behemoths of yore with cheaper, more versatile, much smaller satellites, some no bigger than whiskey-bottle boxes, you need a suitably sized propulsion system.

You don't have to be a rocket scientist to grasp the basic principle of propulsion. Underlying all is what's known in physics as the law of the conservation of momentum. "Combust two gasses," Bailey explains, "expel the hot product out the back, and that pushes the rocket forward. Momentum out one end pushes the spacecraft in the opposite direction."

The same law applies to electrically charged particles, Bailey says, "but instead of hot gasses you throw ions out the back of the spacecraft." Ion thrusters have been around since the 1950s, but not little ones. Industry was clamoring for a solution.

The one Bailey and Perna devised combines lipstick-size tanks of liquid propellant with an array of flat, square, thruster chips that look like cuff links. One chip can generate a thrust roughly equal to the weight of a mosquito. Roger Ramjet would not be impressed. But array those chips in clusters of 36 on tiny satellites, and deploy them in frictionless space, on the fringes of earth's gravity, and that's enough. Plus it's scalable. Liquid-propelled ion thrusters won't replace conventional rocket engines for liftoff, but in theory they could one day propel even the biggest legacy satellites once they're in orbit. "New propulsion technologies don't come along very often," Perna says. "Our technology was new and exciting, and people were interested."

Together they launched Accion Systems in 2012. (There were three other co-founders who have since moved on. Two were foreign citizens who would have had to jump through hoops to satisfy defense customers; the third took another path.) The name they chose combines Accio, the summoning charm Hermione Granger taught Harry Potter at Hogwarts, and ion.

Bailey managed to complete her degree two years later. (The week she defended her doctoral dissertation was the same week Accion closed on its seed round. It was also Christmas. "I was a bad family member that week," she says.) Perna couldn't wait; he put his studies on pause. Whether their gamble pays off depends on how quickly the emerging commercial sector known as New Space achieves liftoff. While countries like China and India are stepping up their investments in space, the United States is pulling back--from a high of more than 4 percent of the federal budget in the mid '60s to half of one percent today.

Commercial investment is growing, but will it grow fast enough? "There's tremendous innovation in this sector," says Will Porteous, a general partner with RRE, a VC firm whose investments include cubesat company Spire, "but some of it looks like science projects and some like real companies."

"The way I think of it," says Bailey, "400 or 500 years from now, if humans are still around, it's probably because we've become an interplanetary species and made it off of the earth. With that kind of long view I think it's a very reasonable field to go into, and to start a company."